Fluids (e.g., oil, water, gas) may exist in a variety of materials, including geological formations. It is often useful to determine the saturation level of a fluid, or of multiple fluids, where one fluid is contaminated by another. However, most available contamination models, such as the nuclear magnetic resonance (NMR)-based models used in the petroleum recovery industry, are designed for miscible fluids (single phase), and may fail when used in immiscible cases. Secondary measurements, such as fluid capacitance and resistivity (which are not always reliable), are sometimes used to refine the estimates derived from the models.